Fair isle question

#1

I am making small wrist bands on dpns in a 1-1 rib with tubular cast on and bind off, and most of the color designs are straight forward enough – simple bands of color so i can just work in one yarn until i have the desired band width and then switch completely to the next color without ever having to float anything.
But a few of the designs i want to make have shapes in contrasting colors that need to be included in the center of the wristband, and i was thinking of using fair isle technique to create them.
My question is: is there a particular way to knit designs in contrasting colors onto a 1-1 rib that will look like what they are supposed to be even when the rib is stretched? Like, is there a way for me to knit a purple circle onto a yellow background and have it look like a circle when it is worn on somebody’s wrist?

edit: I should probably specify that i am not working from a pattern. I am completely winging it.

#2

I’ve never done fair isle on ribbing so I’m not sure. I think it might not be what you’re expecting. Color looks different on purls. Have you tried it? What did you get?

#3

It looked pretty bad. Purls are basically invisible. I’m thinking of maybe knitting the purls where I need to do the contrasting color. It’s probably gonna mess up the stretchiness of the rib in that part but maybe if I start with a couple extra stitches, I can keep the size the same.